ENVR 112 |
| Natural organic matter and bromide/iodide in raw waters react with disinfectant(s) to produce numerous halogenated disinfection byproducts (DBPs). A collective parameter for all the halogenated organic compounds is total organic halogen (TOX), which is regarded as a good indicator for the toxicity of all the DBPs in a water sample. TOX can be measured with the adsorption–pyrolysis–titrimetric method according to Standard Methods 5320B. The first two steps of this method involve concentration of organic halogens from water by adsorption onto activated carbon and removal of inorganic halides present on the activated carbon by competitive displacement by nitrate ions. Since activated carbon can also act as a reductant and, if some halogenated DBPs were reduced to inorganic halides when contacting with activated carbon, they would be removed from the activated carbon during rinsing with nitrate, leading to certain systematic errors for the measured TOX. In this work, whether the reduction of chlorinated DBPs by activated carbon occurs during the TOX measurement and to what extent the reduction affects the measurement of TOX were studied. Initially, a highly dosed chlorinated Suwannee River fulvic acid sample was prepared and dialyzed to reduce the chloride concentration in this sample. The final concentrations of TOX and chloride in this sample were measured to be 1.55 mg/L and 1.72 mg/L, respectively. Then, same doses of activated carbon were added to the aliquots of this sample. After a reaction time of 5 min, 12 h and 24 h, the chloride concentrations in the aliquots were 2.15, 2.44 and 2.64 mg/L, respectively. It indicates that about 20% of chlorinated DBPs adsorbed on the activated carbon was reduced to chloride ions in 5 min. |
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Advances in Drinking Water Disinfection and Disinfection Byproduct Management
8:30 AM-12:10 PM, Tuesday, April 8, 2008 Morial Convention Center -- Rm. 236, Oral
Division of Environmental Chemistry |